Asus Recently released official full final stable Android 6.0 Android Marshmallow update, yet for the official OTA push notification users they need to wait a little bit for the notification to be appeared. For now there official firmware can be downloaded and applied manually to Asus Zenfone 2.

As a asus zenfone 2 user i am not facing any issues after upgrading to Marshmallow from Lollipop, everything works smooth and as far as battery concern it has a quite good battery backup.

Wrong SKU may cause update failure, please update the same SKU version only.

*How to know the device model?
Path: Settings->About-> Model number

**How to know the device software version?
Path: Settings->About-> software information->Build number
***System upgrade may cause part of data missing, please buckup your important data before system upgrading.